I printed out the monthly breakdown and snowball calc numbers and dated them. Should we do a new calculation each month and compare against previous months, or do most of you use an original debt countdown (adding in extra payments as you can make them in the extra payment column)? Does that make sense?

Yes, it makes sense. I did not do a new calculation each month. I just followed the schedule with the number I input at the outset. If you think redoing it in a few months would keep you guys motivated, then it's worth it.